考虑基质渗透性的粗糙单裂隙非达西流动特性研究

Influence of permeable matrix on non-Darcian flow in single rough-walled fracture

粗糙单裂隙及其周围岩石基质是组成复杂岩体裂隙网络的基本单元,了解其中发生的流体流动行为具有重要意义。通过直接求解Navier-Stokes(N-S)方程开展三维粗糙单裂隙和裂隙-孔隙双重介质模型的渗流模拟工作,研究了裂隙表面粗糙度、匹配性和基质渗透性对粗糙单裂隙中发生的非达西流动的影响规律。结果表明:Forchheimer方程可以准确描述双重介质模型中粗糙单裂隙流体流量与压力梯度间的非线性关系;表面粗糙度和不匹配性的增大会加剧裂隙内部开度分布的不均匀性,增大裂隙的流动阻力而促进非达西流动的发生;可渗透基质会使得裂隙过流能力增强,通过粗糙单裂隙的流量最多可增大约14%,这会抑制非达西流动的发生;基质渗透性对裂隙过流能力增长的影响程度与表面粗糙度和不匹配性呈正相关。

Single rough-walled fracture and surrounding rock matrix are the basic units that compose the discrete fracture network,so it is of great significance to study the fluid flow behaviors in it.A series of numerical simulations by directly solving the NavierStokes equation were carried out to study the influence of surface roughness,matching degree and matrix permeability on non-Darcian flow in three-dimensional single rough-walled fracture.The results review that the Forchheimer equation can accurately characterize the nonlinear relationship between the flow rate and pressure gradient in single fracture in fracture-matrix model.The increase of surface roughness and the degree of mismatch aggravates the inhomogeneity of aperture distribution,increases the flow resistance of the fracture and facilitates the non-Darcian flow.By contrast,the permeable matrix enhances the flow through the fracture,and the flow rate through the rough single fracture can be increased by up to 14%,which inhibits the non-Darcian flow.The influence level of matrix permeability on the growth of fracture flow capacity is positively correlated with surface roughness and degree of mismatch.